Merge pull request #4994 from arnetheduck/nim-check-abi

add a simple sizeof checker to compare nim & c types

compiler/ccgtypes.nim

@@ -206,6 +206,10 @@ proc cacheGetType(tab: TIdTable, key: PType): Rope =
   # linear search is not necessary anymore:
   result = Rope(idTableGet(tab, key))
 
+proc addAbiCheck(m: BModule, t: PType, name: Rope) =
+  if isDefined("checkabi"):
+    addf(m.s[cfsTypeInfo], "NIM_CHECK_SIZE($1, $2);$n", [name, rope(getSize(t))])
+
 proc getTempName(m: BModule): Rope =
   result = m.tmpBase & rope(m.labels)
   inc m.labels
@@ -267,6 +271,11 @@ proc getSimpleTypeDesc(m: BModule, typ: PType): Rope =
     result = getSimpleTypeDesc(m, lastSon typ)
   else: result = nil
 
+  if result != nil and typ.isImportedType():
+    if cacheGetType(m.typeCache, typ) == nil:
+      idTablePut(m.typeCache, typ, result)
+      addAbiCheck(m, typ, result)
+
 proc pushType(m: BModule, typ: PType) =
   add(m.typeStack, typ)
 
@@ -656,6 +665,7 @@ proc getTypeDescAux(m: BModule, typ: PType, check: var IntSet): Rope =
       let foo = getTypeDescAux(m, t.sons[1], check)
       addf(m.s[cfsTypes], "typedef $1 $2[$3];$n",
            [foo, result, rope(n)])
+    else: addAbiCheck(m, t, result)
   of tyObject, tyTuple:
     if isImportedCppType(t) and typ.kind == tyGenericInst:
       # for instantiated templates we do not go through the type cache as the
@@ -701,7 +711,9 @@ proc getTypeDescAux(m: BModule, typ: PType, check: var IntSet): Rope =
       idTablePut(m.typeCache, t, result) # always call for sideeffects:
       let recdesc = if t.kind != tyTuple: getRecordDesc(m, t, result, check)
                     else: getTupleDesc(m, t, result, check)
-      if not isImportedType(t): add(m.s[cfsTypes], recdesc)
+      if not isImportedType(t):
+        add(m.s[cfsTypes], recdesc)
+      elif tfIncompleteStruct notin t.flags: addAbiCheck(m, t, result)
   of tySet:
     result = getTypeName(t.lastSon) & "Set"
     idTablePut(m.typeCache, t, result)

doc/nimc.rst

@@ -258,6 +258,10 @@ Define               Effect
 ``ssl``              Enables OpenSSL support for the sockets module.
 ``memProfiler``      Enables memory profiling for the native GC.
 ``uClibc``           Use uClibc instead of libc. (Relevant for Unix-like OSes)
+``checkAbi``         When using types from C headers, add checks that compare
+                     what's in the Nim file with what's in the C header
+                     (requires a C compiler with _Static_assert support, like
+                     any C11 compiler)
 ==================   =========================================================
 
 

lib/nimbase.h

@@ -459,3 +459,7 @@ typedef int Nim_and_C_compiler_disagree_on_target_architecture[sizeof(NI) == siz
 #elif defined(__FreeBSD__)
 #  include <sys/types.h>
 #endif
+
+/* Compile with -d:checkAbi and a sufficiently C11:ish compiler to enable */
+#define NIM_CHECK_SIZE(typ, sz) \
+  _Static_assert(sizeof(typ) == sz, "Nim & C disagree on type size")